預設常數

以下常數由擴充功能定義，因此只有在擴充功能被編譯到 PHP 中，或者在執行時被動態載入後才有效。

XATTR_ROOT (integer)

Set attribute in root (trusted) namespace. Requires root privileges.

XATTR_DONTFOLLOW (integer)

Do not follow the symbolic link but operate on symbolic link itself.

XATTR_CREATE (integer)

Function will fail if extended attribute already exists.

XATTR_REPLACE (integer)

Function will fail if extended attribute doesn't exist.